阴极
材料科学
钠
固溶体
化学工程
纳米技术
化学
物理化学
冶金
工程类
作者
Krishnakanth Sada,Steven Kmiec,Arumugam Manthiram
标识
DOI:10.1002/ange.202403865
摘要
The O‐type layered nickel oxides suffer from undesired co‐operative Jahn‐Teller distortion stemming from Ni3+ ions and undergo multiple biphasic structural transformations during the insertion/extraction of large Na+ ions, posing a significant challenge to stabilize the structural integrity. We present here a systematic investigation of the impact of substituting 5% divalent (Mg2+) or trivalent (Al3+ or Co3+) ions for Ni3+ to alleviate Na+‐ion ordering and perturb the Jahn‐Teller effect to enhance structural stability. We gauge a fundamental understanding of the Mg‐O and Na‐O or Mg‐O‐Na bonding interactions, noting that the ionicity of the Mg‐O bond deshields the electronic cloud of oxygen from Na+ ions. Furthermore, calculations of the Van Vleck distortion modes reveal a relaxation of NiO6 octahedra from Jahn‐Teller distortion and a reduced electron density at the interlayer with Mg2+ substitution. Long‐range (operando X‐ray diffraction) and short‐range (magic angle spinning nuclear magnetic resonance) structural analyses provide insights into reduced ordering, allowing a stable continuous solid solution. Overall, Mg‐substitution results in a high‐capacity retention of ~ 96% even after 100 cycles, showcasing the potential of this strategy for overcoming the structural instabilities and enhancing the performance of sodium‐ion batteries.
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